The overall goal of this proposal is to elucidate the role of N-linked glycans in the maturation and quality control of proteins that traverse the secretory pathway. Carbohydrates play a pivotal role in maturation and degradation of proteins in the cell. The addition of the large hydrophilic and flexible structures to the polypeptide backbone modifies the solubility and stability of proteins. In recent years, N-linked glycans have emerged as the lumenal tags within the secretory pathway that direct the folding, quality control and degradation of nascent glycoproteins by providing attachment sites for resident ER proteins possessing carbohydrate-binding properties. We hypothesize that the position of N-linked glycans on a protein plays an important role in the efficient maturation of glycoproteins in the cell by mediating the timing and location of interactions between the nascent chain and resident ER proteins that assist in the maturation process. Resident ER proteins can protect problematic regions of a maturing protein from premature folding or aggregation, aid in the recruitment of folding catalysts, or the joining of distal domains. Therefore, by controlling the binding of the lectin chaperones calnexin and calreticulin, and the subsequent recruitment of their associated oxidoreductase ERp57, glycans can direct the co- and post-translational maturation of glycoproteins. In addition, N-linked glycans also act as quality control sorting signals within the ER- a type of 'lumenal ubiquitin' that targets aberrant proteins for ER associated-protein degradation (ERAD). Thus, enzymes that regulate the structures of glycans and carbohydrate-binding proteins that recognize specific glycan structures play key roles in directing the protein quality control traffic in the secretory pathway.
The specific aims of this proposal are: (l) to investigate the interplay between glycans and problematic folding regions focusing on the relationship between glycans and vulnerable Cys residues during the folding process; (2) to elucidate the mechanisms by which the lectin ER chaperones calnexin and calreticulin, and their associated foldase ERp57 aid in the maturation of glycoproteins; (3) to characterize the structure and ER maturation pathway of tyrosinase, a model ERAD substrate whose misfolding is associated with albinism and melanoma, by using novel cell biological approaches; (4) to uncover the mechanism by which N-linked glycans direct proteins to the degradative pathway; and (5) to determine the role of he ER resident and putative quality control receptor EDEM in the degradation of aberrant glycoproteins. These studies will provide insights into how proteins are able to fold with high efficiencies in the cell and how the cell degrades aberrant proteins associated with disease states.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
Project #
Application #
Study Section
Cell Development and Function Integrated Review Group (CDF)
Program Officer
Perry, Mary Ellen
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Massachusetts Amherst
Schools of Arts and Sciences
United States
Zip Code
Hebert, Daniel N (2012) An MBoC favorite: Malectin: a novel carbohydrate-binding protein of the endoplasmic reticulum and a candidate player in the early steps of protein N-glycosylation. Mol Biol Cell 23:2236
Tamura, Taku; Cormier, James H; Hebert, Daniel N (2011) Characterization of early EDEM1 protein maturation events and their functional implications. J Biol Chem 286:24906-15
Tamura, Taku; Sunryd, Johan C; Hebert, Daniel N (2010) Sorting things out through endoplasmic reticulum quality control. Mol Membr Biol 27:412-27
Pearse, Bradley R; Hebert, Daniel N (2010) Lectin chaperones help direct the maturation of glycoproteins in the endoplasmic reticulum. Biochim Biophys Acta 1803:684-93
Pearse, Bradley R; Tamura, Taku; Sunryd, Johan C et al. (2010) The role of UDP-Glc:glycoprotein glucosyltransferase 1 in the maturation of an obligate substrate prosaposin. J Cell Biol 189:829-41
Jejcic, Alenka; Daniels, Robert; Goobar-Larsson, Laura et al. (2009) Small molecule targets Env for endoplasmic reticulum-associated protein degradation and inhibits human immunodeficiency virus type 1 propagation. J Virol 83:10075-84
Cormier, James H; Tamura, Taku; Sunryd, Johan C et al. (2009) EDEM1 recognition and delivery of misfolded proteins to the SEL1L-containing ERAD complex. Mol Cell 34:627-33
Wang, Ning; Glidden, Emily J; Murphy, Stephanie R et al. (2008) The cotranslational maturation program for the type II membrane glycoprotein influenza neuraminidase. J Biol Chem 283:33826-37
Pearse, Bradley R; Gabriel, Luke; Wang, Ning et al. (2008) A cell-based reglucosylation assay demonstrates the role of GT1 in the quality control of a maturing glycoprotein. J Cell Biol 181:309-20
Tamura, Taku; Cormier, James H; Hebert, Daniel N (2008) Sweet bays of ERAD. Trends Biochem Sci 33:298-300

Showing the most recent 10 out of 25 publications